A color picture tube has a glass envelope that comprises a neck, a funnel and a faceplate panel. The faceplate panel includes a viewing faceplate that is surrounded by a peripheral sidewall. When the envelope is evacuated, the mechanical stresses in the faceplate panel, caused by vacuum loading, are usually highest at the ends of the major and minor axes, in the interior areas of the panel where the faceplate joins the peripheral sidewall. The juncture of the faceplate and sidewall is usually thick and unyielding. The contour at this juncture is rounded and is commonly referred to as the blend radius.